Back when I was in college, we didn't have graphing calculators. I remember writing a program in my sophomore year that would do my homework for me. Back then, we would have to manually enter points in the equations and then plot them on a piece of paper. After doing about 10 problems that way, I wrote a program that would go through a loop of points, plug them into the equation and then print out the final graph. Next morning I got up and my homework was done. When I turned them in, my instructor asked if he could keep those graphs because they were more accurate than anything he had previously worked with.
A couple of years later I saw a program that would do 2D and 3D charts on the computer, but I haven't seen that application since the graphing calculators became common place. I guess I just haven't kept up on the software side of things. Microsoft came out with v4 of their Mathematics application back in January.